Ellie Goulding is slumped back on a pleather dressing room sofa in the gut of Madison Square Garden, her eyes fixed on a precariously stacked tower of plastic snack bowls as if to say, "I know how you feel." It's day two of her North American tour, and the 27-year-old singer-songwriter has gotten just about no sleep. "God, I'm the most boring person you've ever interviewed," she jokes. Which couldn't be further off.

Goulding has been busy. Herefordshire-born and London-based, she recently wrapped a string of U.K. concerts, arriving in the U.S. not three days later to kick off her spring tour. At the same time, she's promoting the film Divergent, whose soundtrack is speckled with Goulding's vocals, including a new track, Beating Heart, she created specifically for the movie with a music video to match. So, curled up on the couch, she talks about her impending nap like it's dessert a la mode. "I'll just slip that on and be on my way to sleep," she says, pointing to a Simon Preen leotard she plans to wear on stage later that evening. "It makes a great nightie."

Yet two hours later, she's the leader of the pep squad. Revving the audience with refreshingly un-ironic '90s moves and alternating between mic, guitar (acoustic and electric), and drums (air and real), Goulding has sold out the Theater at MSG to 5000 screaming, dancing fans for the second night in a row. (Laughing, she admits she thought it was the "bigger one," the Garden, until right around sound check.) It's not much of a surprise; she's killing every number. But even more so, she knows how to keep her crowd. This is the girl who, after topping the charts, invited her fans to join her outdoor jogs through social media—and who had to stop after they began skipping school en masse to show up.

Part and parcel of her ability to energize with the flip of a switch is that she's clearly having the most fun of all. Maybe it's something to do with her pre-show ritual: "Pushups, jump around, sing, dance, drink, get really hyped with my band so we all have a connection before we go on." Or that she's still genuinely excited about singing. Just after explaining that she strained her voice the night prior, Goulding jolts up at the mention of karaoke (Her go-to song? Why Don't You Love Me by Beyoncé), taking notes on where to reserve a room in K-Town after the show.

Either way, her tour van sounds more exciting than the Spice Bus. "You're all partying downstairs and dancing in the little walkway, and everybody's practically sitting on each other's laps," she says. "This time, it's an all-girls bus, so who bloody knows what's going to happen? We're going to watch films and keep it as homey as possible."

Goulding's also a bit of a hippie—of the dance-if-you-want-to variety more so than the chamsa necklace and on-tour vegan chef kind, though she has both of those things as well. (The chef, a friend, is proving to be a valuable member of the "all-girls bus," having already whipped up kale Caesar salad and veggie sushi in week one alone.) "I generally like music that sounds like it's not from this Earth," she tells me. "First and foremost I love good songs, love songs, but I also am a sucker for music we can all get of hyper to." In addition to Beyoncé, that includes Flosstradamus, Sundara Karma—she takes out her iPod to verify—Arcade Fire, The 1975, Mumford & Sons, Coldplay, Q-Tip, Busta Rhymes, Sean Paul.

For her North American tour, she's traveling with the LA-based artist Conway, who is visually and musically the bleached, blonde pixie cut to Goulding's long, ethereal, golden hair. On the eve of their second performance together, Goulding still hasn't met her opening act in person, but no matter: "This time around we were in such a rush to decide who was going to be the support…I literally listened to a snippet of each song and was like, that's the right vibe," says Goulding. "She kind of stood out." And like that, her edgy counterpoint is inducted.

When it comes to fashion, Goulding has a fairly simple uniform. "A black Acne tee shirt, J Brand leathers, my Doc Martens, and I'm set," she says, also professing devotion to Alexander Wang, Nasty Gal, Simon Preen, and Jeffrey Campbell—plus a good hunk of carbon. "I'm a real sucker for diamonds," she says.

Though Goulding is best known for her original club ballads, it's hard not to notice the cover work she's been doing recently. So far, this tour's set list has included masterful renditions of James Blake's Life Round Here, Elton John's Your Song, and an adrenalized drum solo over some blaring M.I.A. "No more covers," she says at first about the subject, but just before moving on she admits, "I just did a cover, a new one. I imitate opera singing, which I love to do." Did she study opera? "No, but I pick up on people's vocal inflections, and then I just sing all day—which I shouldn't do." Goulding takes out her iPod again and scrolls to E, adding, just before hitting play, "but it's a secret." She closes her eyes and conducts while listening to her voice climb higher and higher in an operatic vibrato. "I'm gonna get this bloody note coming up," she exclaims, squinting, as though scared the recording might not make it this time around. Then she breathes out, victorious.

The track in question is one she recorded a few weeks ago in her London studio. To date it doesn't have much of a plan or a home on her next album, but when you hear it, you'll agree: the girl deserves a nap.